Am 26.03.2014 22:33, schrieb Christian Kanzian: > Am Mittwoch, 26. März 2014 schrieb jerome: > >> So is this normal ? >> I mean, core use and the fact I need export only one at time ? >> >> Sorry for long story but it help to understand how and why. >> >> And sorry for my bad english ;) >> >> Thanks to all > > Within OpenCL the GPU does the parallel thing for you. > > There is a blog post on that [0]. According to that you have to set "export > multiple images in parallel" to 1. BTW this setting was removed sometime ago > from the GUI or I can't find it anymore.
That's mostly correct. If you set that option (parallel_export) to something higher than 1 darktable starts that many export threads in parallel. Any available OpenCL device gets allocated to one of the parallel threads, all remaining threads are processed on CPU. If you have two GPUs with the same speed, it makes a lot of sense to set parallel_export to 2. However, in most cases users have only one GPU that is often much faster than the CPU. Or few people have two GPUs with a big performance difference. In these cases you only profit from multiple parallel export threads, if you export *many* images in one step. In case of few images to export you always need to wait until the slowest device is finished and it often be faster to process all of them on the fastest device only. @Jerome: what was said before, only should affect the speed. In your case it seems that export hangs at some point. You should start darktable with option '-d opencl' to see what happens. If you share that debug output here we might be able to help. Does your system completely freeze? The power supply of your computer needs to be strong enough to feed two GPUs in parallel. If not, voltage will drop and you may get a hardware crash. Ulrich ------------------------------------------------------------------------------ _______________________________________________ darktable-devel mailing list darktable-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/darktable-devel
